1. Field of the Invention
The invention relates to a device for coating cylinder walls of an internal combustion engine forming a plurality of cylinders.
2. Description of Related Art
For reasons of weight, internal combustion engines in motor vehicles are regularly designed with an engine block made of light metal, in particular aluminum. However, it can prove problematic here that, due to the tribological properties of the light metal, in particular the comparatively poor resistance to wear, the inner walls of the cylinders formed by the engine block are only inadequately suitable as running surfaces for the pistons.
In order to avoid these problems, in many internal combustion engines with an engine block made of light metal cylinder liners made of, for example, grey cast iron are used, as a result of which the advantages of the light metal (low specific weight) can be combined with those of the grey cast iron (good tribological properties).
Alternatively, it is known for the running surfaces of the light metal engine blocks to be provided with a coating in order to realize the desired tribological properties for the running surfaces. Such a coating is regularly realized by melting the coating material and spraying it onto the cylinder walls.
A variety of different coating methods are known, with thermal coating methods, in which the coating material is melted and then—usually by means of a compressed air or other gas flow—atomized and transported onto the surface which is to be coated, being used in particular. Known thermal coating methods include, for example, plasma coating, high velocity oxy-fuel spraying and wire arc spraying.
A device for wire arc spraying is for example known from DE 198 41 617 A1. The device disclosed therein is based on a spray lance which is driven so as to rotate around its own axis and at the same time is advanced in the direction of the longitudinal axis, so that this can penetrate to varying depths into the cylinder which is to be coated. The spray jet of coating material generated by the spray head of the spray lance is thus applied to the cylinder wall in question in a helical movement.
In the known coating methods for cylinder walls of an internal combustion engine, the coating of the individual cylinders takes place in succession. In particular, this allows the complexity of construction and thus the costs of the coating installation to be kept low. However, one disadvantage here is the relatively long processing time which is necessary in order to coat all the cylinders of a multiple-cylinder internal combustion engine.